Spark plug



Aug. 2, 1949.

W. A. BYCHINSKY `ET AL S PARK PLUG Filed Nov. 1, 1945 I a7 4 W all '$41.

Patented Aug. 2, 1949 SPARK PLUG Wilfred A. Bychinsky and Walter L. Church, Flint,

Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 1, 1945, Serial No. 626,020

9 Claims.

This invention has to do with spark plugs incorporating an ignition coil or transformer. Such plugs have been found te be particularly desirable in ignition systems used on internal combustion engines employed in aircraft. The plug here disclosed is especially designed for use in the high frequency ignition system described and claimed in the Patent 2,459,297 of Lucian B. Smith, dated January 18, 1949, and filed concurrently herewith, said system being characterized by distribution of current to the plugs at low voltage where it is stepped up to the high voltage required for ignition by transformers associated with each of the spark plugs. The diiiicult problems arising from high voltage distribution, such as flashover at high altitude, deterioration of the wiring harness by corona discharge and leakage of current through the capacitance of the ignition cable, are thereby avoided. The arrangement also makes it possible to shield the circuit much more easily so as not to interfere with radio communication.

An important feature of the invention is the compact but efficient high tension transformer built into the plug. The transformer is of such construction as to withstand the relatively high temperatures encountered at the plugs. The spark plug and its shield are especially designed to receive the coil and form a compact unit assembly which may be as readily replaced as a conventional plug.

Various other features of the invention will be disclosed in the following description with the aid of the accompanying drawing which is a sectional View through the spark plug and associated parts.

Referring to the drawing, 30 indicates the spark plug shell in which is mounted insulator 32, preferably of an aluminum oxide base composition. The insulator 32 is provided with a central bore increasing in diameter by stages from the electrode and upwardly. In the lowermost portion of the bore there is provided a platinum tip 34 having its upper ilanged end supported on a shoulder formed in the insulator bore as shown. The bore above the tip is filled with silver 35 which is cast in place and holds the platinum tip in position. Above the silver is a conducting glass seal 38 fused in place. Embedded in both glass seal 38 and silver core 36 and acting to make metallic contact between the two is coiled wire, preferably nickel,

40. Above seal 38 is seal 42 which may be of a composition similar to seal 38. Seal 42 surrounds and grips the upper electrode element 44. Parts 34, 36, 38, 40, 42 and 44 together constitute the center electrode of the spark plug.

Within the uppermost portion of the bore is arranged the transformer P'S comprising a core 46 of powdered iron, the particles being held together but electrically insulated from each other by a suitable insulating varnish or other compound so as to minimize eddy current losses. Around the core is wound the primary P', the upper end of which is grounded as at 48 to the shell of the spark plug through metal gasket 69, lock washer El, annular member 68 and sleeve 64, secured to the shell. The lower end of primary P' extends upwardly through the central aperture in the core and is connected as by welding to metal contact 50. The core and the primary winding are housed within insulator 52 preferably of heat resistant material such as a steatite provided with spaced circumferential ribs 54. Secondary S is wound in a series of connected pancake coils, each of which is housed in one of the grooves formed by the ribs of the insulator. The purpose of this is, of course, to reduce the distributed capacity thereby providing higher voltage output with a smaller coil and reducing the possibility of shortcircuiting of turns without employing bulky insulation between the layers. The upper end of the secondary S is grounded as indicated at 56 While the lower end is connected to metal contact disc 60. The wire of the secondary coil S is preferably insulated by glass yarn impregnated with silicone resin. The impregnation is accomplished under vacuum and is followed by heat treatment. The coil spring 62 establishes electrical connection between the contact disc 52 and the upper end 44 of the center electrode.

The transformer described is assembled as a unit and inserted in the upper end of the bore of the insulator 32. The insulator 32 is secured within the shell 28 by means of a sleeve 64, the lower end of which telescopes over the upper end of the shell and is permanently secured thereto as by silver soldering. If preferred, the parts may have a threaded connection. A suitable gasket 65 of soft metal such as aluminum may be provided between the sleeve 64 and the upper end of the insulator. Within the sleeve 64 is secured by threaded engagement or by staking, annular member 63 the lower end of which bears upon spring-like look washer 6l resting on soft metal gasket B9 engaging the upper end of the insulator 52 of the transformer as shown. It is to gasket 69 that the ground connections of the primary and secondary are made as previously described.

Member B8 is provided with inwardly extending flange 10 serving as an abutment for apertured insulator 'l2 which is held in position by spring 'i4 1 surrounding a split tubular metal jack S0 having 3 a flanged lower end engaged by the spring and held by Yit in engagement with the contact 50 of the primary P of the transformer. Within the jack 9G there is engaged a plug 94 secured to the end of spark plug cable 96. Any suitable means may be provided to secure the cable and its plug or terminal 94% in position in the jack and to insulate it `)from surrounding conductor-s and as this constitutes no part of the present invention it'will not be described in detail. The cable may be provided with conventional radio shielding consisting of tube 98 carrying the fitting 80 whichmay be clamped to the upper end of the sleeve 64 by means of an apertured nut .vl-82 as shown. -Inthe arrangement illustrated the itnreaded :portion of nut It?? may be split as shown and `may ibeeprovided with a nut E94 adapted to be turned Vdownen external threads on the nut |02 to lock it in Dosition.

The spark plug and coil form a permanent assembly which is replaceable as a unit just like v a Yconventional plug. By housing the transiormer within .the insulator 3?. it is insured vthat there will .be no .short-circuiting, particularly at high .altitudes by discharge between the secondary S' and the surrounding spark .plug shell.

The spark plug is susceptible of considerable modilication. For example, if desired, thecenter electrode of the plug may embody a built in resistance as described 4and vclaimed in prier ap- .plication Serial No. Li88,l1l, filed May ,24, `1943, by 'laine McDougal .et al., now Patent No. y2,459,- 282.

We claim:

1. ,A .spark plug comprising a cylindrical shell,

otherend being in conducting relation with a terf iminal adapted t0 vmake contact with the spark plug lead, a cup-shaped insulator surrounding the primary windinghaving axially spaced annular .ribs formed thereon, and a secondary winding comprising connected coils Voccupying the -spaces vbetween said ribs, one end Aof said vsecondary be- 'ing in conducting relation .with the central electrode and the other end with the said shell.

v2. A spark plug comprising a cylindrical shell,

1an integral insulator withinV the shell having a l central bore therein, an electrode sealed within the lower end of the insulator, said shell being provided at its lower end with an electrode cooperating therewith and a transformer lwithin the upper end rof the bore of said insulator comprising a core composed of magnetic particles, a primary winding about the core, one end of said winding lacing .grounded to the shell and the other end being in conducting relation with a terminal adapted to make contact with the spark pluglead,

. :a cup-shaped insulator surrounding the Vprimary winding having axially spaced annular ribs formed thereon and a secondary winding compnising connected coils occupying the spaces between said ribs to form a pancake winding there- Qn, one-end Vof said secondary winding being in conducting relation with Vthe central electrode and the other end with said shell.

3. A spark plug comprising a cylindrical shell,

.an integral insulator withinthe shell having .a

a transformer within the .y

Cil

central bore therein, an electrode sealed within the lower end of the insulator, said shell being provided at its lower end with an electrode cooperating therewith and a transformer within the upper end of the bore of said insulator comprising a core composed of magnetic particles, a primary winding about the core, one end of said winding being grounded Yt'othevshell and the other being Yin conducting relation with a Aterminal adapted to make contact with the spark plug lead,

.a cup-shaped insulator surrounding the primary ,winding having axially spaced annular ribs formed thereon and a secondary winding comprising connected coils occupying the spaces between said ribs,.one.end of :said secondary winding being connected -to a metallic disk recessed in the end of said cup-shaped member in conducting relation with the central electrode and the other end connected to said shell.

4. A spark plug comprising a cylindrical shell,

integral Vinsulator within Athe :shell having a `central bore therein, :an electrode sealed vwithin .the lower .end .of the insulator, said lshell ,being proyided at its lower .end with an `electrode cooperating Itherewith and a .transformer within .the upper end of the bore ,comprising a .core composed of insulated metallic particles, a primary winding Vabout the core, ,one vend of .sai-d winding :being in conducting relation with a terminal vadapted to .make `contact with .the spark plug lead, .a eupshaped .insulator ,surrounding .the .primary winding having axially spaced annular ribs Aformed .thereon and a secondary windingcomprisng `connected coils occupying the spaces between `said ribs, oneend of said secondary winding'being con-- nected to a metallic disk of lsubstantial thickness recessed 'in the enclof said cup-shaped member .in .conducting relation with the .central electrode and the other end connected .to said shell.

.5. A spark plug comprising a tubularshell `hav.- ing a .ground electrode in the lower end ,thereof, an .integral Vinsulator .housed within the vshell having .a central bore, the upper .end `of which is enlarged, a central `electrode sealed in .the lower end of the v,bore and cooperating with .the ,ground `electrode to form a spark gap, Aa transformer housed Within the upper enlargedportion .of the boreinsaid insulator comprising a Ametallic core composed of insulated metal particles, .a .primary winding surrounding the core and having A one .end in conducting relation with the shell and vthe -other-end in vconducting relation with a terminal adapted to make contact with the sparkplug lead, a .cup-shaped .insulator surrounding the .primary winding, said insulator .havingaxially spaced annular ribs formed thereon and ya secondary winding comprising connecting coils occupying .the spaces 4between said ribs, said secondary winding being connected at :one end to a metallic disk Aci substantial thickness recessed in the ,endof said cup-shaped member and in conducting Arelation with the said central electrode and at the other end with said shell.

6. A spark plug comprising a'tubular shell hav-- ing ,a ground electrode in the `lower end thereof, an integral insulator housed within the shell .haying a central bore, the upper end of which is -enlarged, a central electrode sealed in the lower end vofthe bore `and cooperating with .the ground electrode to form a spark gap, a transformer housed within the upper enlarged portion Aof thefbore in saidinsulator comprising a core of adhering :metal :particles :insulated from each other, a primary winding surrounding said core and having one end in conducting :relation Vwith .the shell and the other end connected to a conductor centrally disposed in said core and in conducting relation with a terminal adapted to make contact with the spark plug lead, a cup-shaped insulator surrounding the primary winding, said insulator having axially spaced annular ribs formed thereon and a secondary winding comprising connected coils occupying the spaces between said ribs, said secondary winding being connected at one end to a metallic disk of substantial thickness recessed in the end of said cup-shaped member and in conducting relation with the central electrode and at the other end with said shell.

7. A spark plug comprising a tubular shell having a ground electrode in the lower end thereof, an integral insulator housed within the shell having a central bore, the upper end of which is enlarged, a central electrode sealed in the lower end of the bore and cooperating with the ground electrode to form a spark gap, a transformer housed within the upper enlarged portion of the bore in said insulator comprising a core of adhering metallic particles insulated from each other, a primary winding surrounding said core and having one end in conducting relation with the shell and the other end connected to a conductor centrally disposed in said bore and in conducting .relation with a terminal adapted to make contact with the spark plug lead, a cup-shaped insulator surrounding the primary winding, said insulator having axially spaced annular ribs formed thereon and a secondary winding comprising connected coils occupying the spaces between said ribs and forming a pancake winding, said secondary winding being connected at one end to a metallic disk of substantial thickness recessed in the end of said cup-shaped member and in conducting relation with the central electrode and at the other end with said shell.

8. A spark plug comprising a tubular shell having an integral insulator housed therein, said insulator having a central bore the upper end of which is enlarged, a central electrode sealed in the lower end of the bore, a transformer housed within the upper enlarged end of the bore comprising a metallic core, a primary winding surrounding said core, having one end grounded to said shell and the other end in conducting relation with a terminal adapted to make contact with the spark plug lead, a cup-shaped insulator within which said primary winding and core are disposed, said cup-shaped insulator having axially spaced annular ribs formed thereon, a secondary winding comprising connected coils occupying the spaces between said ribs, one end of said secondary winding being in conducting relation with the central electrode and the other end with the shell, an annular member recessed in the upper end of said shell for sealing said secondary Within the upper enlarged end of the bore of said insulator and means cooperating with the upper end of said shell for clamping said annular member in said shell and connecting an insulated and shielded lead to the primary of said transformer.

9. A spark plug comprising a tubular shell having an integral insulator housed therein and a ground electrode in the lower end thereof, said insulator having a central bore the upper end of which is enlarged, a central electrode sealed in the lower end ofthe bore and cooperating with said ground electrode to form a spark gap, a transformer housed within the upper enlarged portion of the bore in said insulator comprising a core of adhering metal particles insulated from each other, a primary winding surrounding said core and having one end in conducting relation with the shell and the other end connected to a conductor centrally disposed in said core and in conducting relation with a terminal adapted to make contact with the spark plug lead, a cupshaped insulator surrounding the primary winding, said insulator having axially spaced annular ribs formed thereon, a secondary winding cornprising connected coils occupying the spaces between said ribs and forming a pancake Winding, said secondary winding being connected at one end to a metallic disk of substantial thickness recessed in the end of said cup-shaped member and in conducting relation with the central electrode and at the other end with said shell, an annular member recessed in the upper end of said shell for sealing said secondary within the upper enlarged end of the bore of said insulator and means cooperating with the upper end of said shell for clamping said annular member in said shell and connecting an insulated and shielded lead to the primary of said transformer.

WILFRED A. BYCHINSKY. WALTER L. CHURCH.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,008,351 Merritt Nov. 14, 1911 1,164,113 Orswell Dec. 14, 1915 2,266,614 Robinson Dec. 16, 1941 2,392,171 Marsh Jan. 1, 1946 2,414,692 Harkness J an. 21, 1947 Certicate of Correction Patent No. 2,478,087 August 2, 1949 WILFRED A. BYCHINSKY ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 5, line 27 claim '7, for the Word bore read core;

and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 13th day of December, A. D. 1949.

[EAL] THOMAS F. MURPHY,

Assistant Oommz'aszaner of Patente.

Certificate of Correction Patent No. 2,478,087 August 2, 1949 WILFRED A. BYCHIN SKY ET AL. It is hereby certified that error appears in the printed specification of the above numbered patent requlring correction as follows:

Column 5, line 27, claim 7, for the Word bore read core;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the oase in the Patent Office.

Signed and sealed this 13th day of December, A. D. 1949.

THOMAS F. MURPHY,

Assistant Uommz'asz'oner of Patents. 

